‘Unforgotten’: A cold case tests old friendships

A third season of cold case investigations and emotional roller coasters in “Unforgotten” airs Saturdays at 9 p.m., beginning Sept. 14 on Arizona PBS.

Set in the southern part of England, this season’s case involves a missing 16-year-old girl whose body is found near a London motorway. The police investigation failed, and detectives Cassie Stuart and Sunil “Sunny” Khan are determined to find the truth. Nicola Walker and Sanjeev Bhaskar reprise their respective roles as detectives Stuart and Khan.

When human remains are found by a motorway near London, Cassie and Sunny are called to the scene. Dogged work leads the team to Hayley Reid, a 16-year-old girl who went missing on the eve of the millennium. The police’s failure to find out what happened to Hayley wrecked her family’s life. Cassie’s compassion makes her determined to correct the mistakes made by the original investigating team – whatever the cost to herself. A close-knit group of old school friends hold the key to what happened. Doctor Tim Finch, television host James Hollis, failing salesman Pete Carr, and artist Chris Lowe. As the four suspects find themselves under the spotlight, their tight bond is put to the test. They all have secrets in their past – events that have pulled their lives apart. None of them are quite who they first seem to be, but is one of them capable of murder?

WATCH: Catch up on the most recent episodes, or enjoy the whole series via Passport.